The newly analyzed skull, reported online this week in the journal Proceedings of the National Academy of Sciences, adds to the heated discussion.

Modern and Archaic

The skull was discovered in a cave in southwestern Romania and is at least 29,000 years old. A jawbone found nearby with similar morphological traits is dated to 40,500 years ago. The researchers conclude both specimens are about 40,000 years old.

Comparisons to other skulls suggest the Romanian skull clearly belongs to a modern human, said paper co-author Erik Trinkaus, an anthropologist at Washington University in St. Louis, Missouri.

"But some characteristics are extremely unusual and rather archaic," he said.

For example, the forehead is "extremely long and flat" when compared to modern humans from western Europe and Africa, Trinkaus said. And the molars are the largest ever documented for modern humans.